Pathological nerve patterns in human basal cell carcinoma

The peculiar combined, or binary involvement of epithelium and stroma makes basal cell carcinoma (BCC) a unique tumour. Nerve fibres have been shown to play an active role in different cancers. A prospective observational study was carried out on punch biopsies harvested within BCC surgical excision specimens. A total of 10 samples of histologically diagnosed BCC, derived from 10 different patients (five females, five males), was included in the study. Within the BCCs, seven different histological sub-types were identified: morphea-like, basosquamous, micronodular, mixed nodular-micronodular, adenoid, nodular and superficial multifocal. Nerve fibres were stained for indirect immunofluorescence targeting protein gene product 9.5. Three different morphological patterns of nerve fibre distribution within the BCCs were identified. Pattern 1 displayed a normal skin nerve pattern, in which the fibres were dislodged by the growing tumour masses. Pattern 2 featured a ball of curved, tangled nerve fibres close to the tumour masses, slightly resembling piloneural collar nerve fibres, wrapped around hair follicles in the normal anatomical setting. Pattern 3 showed nerve fibres crowding in the sub-epidermal layer with focal epidermal hyperinnervation. Such a pattern is reminiscent of the typical anatomical neuro-epithelial interaction in mechanosensory organs. Our study may disclose a hidden third player, of nerves. Thus, tissue involvement of BCCs may be better represented by the triad of epithelium, stroma and nerves, each component retaining some features associated with its developmental setting.